Bradski already answered it, but a little clarification is in order.
What do you mean by “fornication”? Performing sex outside a catholic, sacramental marriage? Or performing sex outside some christian marriage? Or performing sex outside some “formal” secular marriage? Let’s not forget that “formal” marriage ceremonies were not universal since the time of cavemen - on the very contrary. There were tribal marriages, morganatic marriages, matriarchal societies (mater semper certa, pater semper incertus est), etc… all sorts of semi-formal or formal arrangements… Which ones are considered “fornications”? (Side note: “how do you know that the sex among the hippies were without love?”.)
It is a usual error to forget that sexual activities were around way before Christianity emerged.
Yes, that’s easily recognizable, but when Christ came, one of the things that ended up doing was setting up what a marriage should be, but it is easy said that it should be kept by His followers (us Christians). If a baptized guy went into any of those (except the one-man-one-woman permanent marriage), he’d get into a sin trouble, as he’s probably professed his faith as a Christian to God (except if he was an infant, but bear with me here). If you’re not a Christian, you may be contested for lack of proper morality by those that are, but if you haven’t taken the proper “plan” to salvation, nothing really changes in you. At that point it doesn’t really matter if it’s fornication or not, you either never been in communion with God and the Church, or you’re excommunicated for renouncing your faith.
How about this?
“I believe SOME, especially young men have pre-marital sex because it boosts the ego.” Though I would think that the good feeling coming from having sex is more important than an ego-boost (The phrase “a fate worse than death” is out of fashion these days.

). Not to mention their red-hot libido is “breathing down” on their necks (to be a tad poetic). But the phenomenon is too complex to be reduced to a few sound bites.
By the way,
it is a limited christian concept that “fornication” is inherently “bad” (and many christians reject this idea). Since many (or maybe “most”?) people see nothing wrong with the practice, their opinion is not constrained by certain teachings.

As for the last few questions of the OP (“To serve others? or the “me”?”), the answer would be: “A correct balance between the two”. Extremes are usually unhealthy. Total selfishness is as dumb as total selflessness.
What I’ve put in bold on your statements doesn’t say that some act is still morally incorrect, at all. Culture doesn’t mandate what’s good from bad, unless you want to fall into some flawed relativism. Christians feel like there’s nothing bad on it because the culture feels like saying so and they follow the trend, probably to just be in-sync with the “morals” that are applied to the 21st century (you know the usual statements, “blah, blah, blah, blah, but we’re in the 21st century!”, implying that any morals have been acquired through time… They were actually lost), or to avoid getting mocked for having a different view on it (most aren’t really able to face that type of discrimination, which does happen from time to time.
But as a former atheist myself, I’d say that sexuality is really, really valued here. Christians see this as an act that makes two persons become one in love and passion, and as we believe that marriage is permanent, this act should be only done by those that love each other so much that they made vows granting they wouldn’t not separate until they are widows.
So yeah, we really don’t diminish the act, we give it value. And hey, research says religious people enjoy it more than non-religious (not in the Catholic sense of religious. That’s… even worse xD) people, go figure. It actually works
